Embodiments of the present invention are directed generally to cable network fault isolation and more specifically to the identification of faults in devices comprising a video on demand service in a hybrid fiber coax (HFC) cable network.
Cable networks deliver voice, data, and video to subscribers over a complex network of headends, regional data centers, hubs, and nodes. At the upstream terminus of the network is the headend and regional data center. Typically, a headend comprises the analog and digital video signal processors, video on demand systems, and other video content management devices. A regional data center comprises digital service management devices (e-mail servers, DNS, and Internet connectivity) and routers that interconnect the regional data center with a headend. A hub receives the video and data signals from the headend and regional data center, processes these signals through appropriate modulators, and sends these signals downstream to a hub. The hub provides the signals to a node that is ultimately associated with individual subscribers. A node provides an interface between the fiber-based component of the HFC cable network and the RF/cable component of the network that is the transport media to the home.
In a commercial network, a headend may service multiple hubs and a hub may service multiple nodes. A regional data center may provide digital services to multiple headends. From a node to the home, the RF/cable component of the HFC cable network may branch numerous times. Amplifiers, line extenders, and passive devices are employed to maintain signal quality across all branches (or “cascades”) serviced by the node.
HFC cable networks are increasingly dependent on two-way data transport. Video on-demand or VOD services rely on out-of-band (OOB) channel signaling or a DOCSIS-compliant data channel to obtain requests for video content from a subscriber's set top box. In a typical configuration, the VOD service makes available to its users a selection of multiple video programs that they can choose from and watch over a network connection with minimum setup delay. At a high level, a VOD system consists of one or more VOD application servers that pass and/or store the relevant content; one or more network connections that are used for program selection and program delivery; and customer premises equipment (CPE) to receive, decode and present the video on a display unit.
The most common CPE for VOD is an addressable STB that provides the functions of receiving cable signals by tuning to the appropriate RF channel, processing the received signal and outputting VOD signals for viewing on a display unit. Such an STB also typically hosts a VOD application that enables user interaction for navigation and selection of a VOD menu.
FIG. 1 illustrates a video-on-demand provision system as known in the prior art. The various components of the network 100 include (i) one or more data and application origination points 102; (ii) one or more application distribution servers 104; (iii) one or more VOD application servers 105, and (iv) customer premises equipment (CPE) 106. The distribution server(s) 104, VOD application servers 105 and CPE(s) 106 are connected via HFC cable network 101.
The application origination point 102 comprises any medium that allows an application (such as a data download application or VOD-based application) to be transferred to a distribution server 104. This can include for example an application vendor website, CD-ROM, external network interface, mass storage device (e.g., RAID system), etc. Such transference may be automatic, initiated upon the occurrence of one or more specified events (such as the receipt of a request packet or ACK), performed manually, or accomplished in any number of other modes readily recognized by those of ordinary skill in the art.
The application distribution server 104 comprises a computer system where such applications can enter the network system. Distribution servers are well known in the networking arts, and accordingly are not described further herein.
The VOD application server 105 is a computer system where on-demand content can be received from one or more data sources 102 and enter the network system. These sources may generate the content/data locally, or alternatively act as a gateway or intermediary from a distant source. The VOD application server 105 includes the Session Resource Manager (SRM) functionality, and asks the network control system (NCS) for resources. The NCS responds with a negative or positive response to the request, and the VOD application server implements the appropriate resource allocation logic.
In U. S. cable systems, downstream RF channels used for transmission of television programs are 6 MHz wide, and occupy a 6 MHz spectral slot between 54 MHz and 860 MHz. Deployments of VOD services have to share this spectrum with already established analog and digital cable television services. For this reason, the exact RF channel used for VOD service may differ from plant to plant. However, within a given cable plant, all homes that are electrically connected to the same cable feed running through a neighborhood will receive the same downstream signal. For the purpose of managing VOD services, these homes are grouped into logical groups typically called service groups. Homes belonging to the same service group receive their VOD service on the same set of RF channels.
Several specific frameworks exist in the prior art for provisioning on-demand (e.g., VOD) and similar services to network subscribers. Notably, in the cable network context, the Interactive Services Architecture (ISA) specification (see, e.g., ISA Versions 1.4 and 1.5) published by the Time Warner Cable describes techniques and mechanisms for distributing and delivering movie titles for VOD services. The ISA specification defines functional roles and interfaces that enable the development of pluggable interactive services in a cable environment. The focus of the ISA is primarily on viewer services, which are defined as the set of functions provided by the cable operator to its customers.
Content (e.g., audio, video, etc.) is provided in each downstream (in-band) channel associated with the relevant service group. To communicate with the headend, the CPE 106 uses the OOB or DOCSIS channels and associated protocols.
The provision of VOD services may fail as a result of faults in any of the components and communication paths described above. What would be useful is a system and method for determining that a fault affecting multiple subscribers has occurred and for identifying the probable cause and location of that fault.